1. Field of the Invention
The present invention relates to an electronic component manufacturing method which includes a step of embedding a metal film.
2. Description of the Related Art
Conventionally, the semiconductor integrated circuit has been using a gate first method which is a method of performing processing by etching after having formed a gate insulating film and a gate electrode on a wafer surface. Recently, a gate insulating film of a MOSFET becoming thinner as the element is miniaturized, and, when an SiO2 film is used for the gate insulating film, tunnel current is generated for a film thickness of 2 nm or smaller which is a recently required value, and gate leak current is increased. Accordingly, it is being studied recently to replace the gate insulating film material by a high-permittivity material which has a relative permittivity higher than that of the SiO2 film. By this method, an SiO2-converted film thickness (EOT: Equivalent Oxide Thickness) can be made smaller even when the actual thickness of an insulating film is made larger. In a recent MOSFET having a gate length of 22 nm or smaller, however, the EOT is required to be reduced further. For satisfying this requirement, it is necessary to increase the actual thickness of the insulating film by using the high-permittivity material to reduce the gate leak current. In the gate first method, however, source/drain formation step is performed after gate formation and thereby the gate insulating film and the gate electrode are heated to cause heat diffusion between the insulating film and the metal film due to the heating, and there is arising a problem that mobility degradation and an operation voltage (Vt) shift occur.
Accordingly, for solving these problems, there has been carried out energetic research and development for a gate last method which forms the source/drain in advance and forms the gate insulating film and the gate electrode lastly. In this method, since the gate part is formed lastly, the heating temperature applied to the gate part can be made lower and probably it is possible to suppress the mobility degradation and the operation voltage (Vt) shift which have been the problems in the gate first method. Subjects of the gate last method are to deposit various kinds of metal thin film in a shape having an opening of 22 nm or smaller and a depth of 22 nm or larger (hereinafter, called a trench), and to control the film thicknesses of the material deposited on the side wall and the bottom part of the trench to desired values, respectively. Further, since the various kinds of metal thin film are stacked, it is also necessary to suppress mutual diffusion between the metal thin films.
In the gate last method, the method of forming the various kinds of metal thin film material includes a CVD (Chemical Vapor Deposition) method, an atomic layer adsorption/deposition method, and a sputtering method. The CVD method has problems in film thickness controllability, surface uniformity, and reproducibility, since an incubation time exists in the forming process. The atomic layer adsorption/deposition method has excellent film thickness controllability, but, when a thick film is formed, a growth time becomes long and a cost problem occurs because an expensive source gas is used. Each of these methods using the chemical reaction of source gas can form a film uniformly not only on the bottom part but also on the side wall of the trench, but, on the other hand, the trench comes to have a narrower opening when the deposited film thickness is made larger. As a method of solving these problems, there is proposed a method of forming the various kinds of metal thin film material by a sputtering method which has excellent film thickness controllability, surface uniformity, and reproducibility.
Japanese Unexamined Patent Application Publication (Translation of PCT Application) No. 2004-506090 discloses an apparatus which can form a film also on the side wall of the trench part as the CVD by performing sputtering at a high pressure of 1 Torr or higher. In this method, the directivity of a sputter ion against a wafer surface is suppressed by the sputtering at a high pressure and thereby it is possible to form a film also on the side wall of the trench part. Japanese Patent No. 3193875 discloses a technique and an apparatus in which a Seed-Al layer is formed by a sputtering method for accelerating Al film migration after a barrier underlayer stacking Ti and TiN has been formed and Al is caused to migrate at a high temperature to be embedded. This method shows that it is possible to embed Al into the trench while suppressing Al diffusion by the barrier underlayer stacking Ti and TIN.
As described above, in the recent film formation on an extremely fine pattern, various kinds of metal thin film are stacked and thereby the reduction of a trench opening diameter is caused. Accordingly, it is necessary to use a metal thin film formation technique which can suppress the reduction of the opening diameter as far as possible even when the various kinds of metal thin film are stacked. Further, it is clear that the Al embedding deteriorates the characteristic of a metal film used in the gate electrode part by the Al diffusion, and thereby an extremely-thin film barrier layer forming technique is required for suppressing the Al diffusion.
However, each of the above described techniques has the following problem.
The method of sputtering at a high pressure of 1 Torr or higher, which is disclosed in Japanese Unexamined Patent Application Publication (Translation of PCT Application) No. 2004-506090, can form a film onto the trench side wall, but has a problem that the trench opening becomes narrower when the trench opening is made smaller as 22 nm or smaller. Further, the method of Al embedding, which is disclosed in Japanese Patent No. 3193875, has a problem that a thick barrier film stacking Ti and TiN is required to be formed for suppressing the Al diffusion. Moreover, since the Seed-Al layer is further formed on the barrier film stacking Ti and TiN for accelerating the Al migration, there is a problem that the trench opening is narrowed.